As for the GTI vs R comparison, we knew the R was going to be faster even if its lesser brother receives some tuning bits to boost the 2-liter engine to the same 300 PS output or even slightly higher.
Oh, and let's not forget that Volkswagen makes it abundantly clear which of these Golfs is the fastest. With DSG, the Golf R takes 4.9 seconds to reach 100 km/h, which comes down to 5.1s if you want a stick. The GTI Performance Pack takes 6.4 seconds to reach the same speed, while the GTD requires 7.5 seconds. In both these cases, the gearbox you have doesn't make a difference.
The diesel model compensates for its bad performance with more torque and about a third less fuel consumed. But because of the TDI engine, it's slightly heavier even than the AWD Golf R model.
While we are on the subject of pros and cons, the AWD system on the R eats up about 40 liters of trunk space. Its suspension is lower by about 10mm and also stiffer. All three models can be configured with adaptive suspension and have a standard Soundaktor systems that resonates sound into the cabin when in sports mode.
There's a reason we know so much, and that is the fact that all hot Golf models were launched in 2013. There are so many things Top Gear could have done instead of this. We have no shortage of suggestions. For example, people might want to see the difference between an Audi TTS and a Golf R - same engine and gearbox, not the same weight and traction.
Another idea would be to pit the Golf GTD against the Ford Focus ST diesel. Both models have wagon versions, which many people buy but few magazines have tested.